Fluid batch hydroforming process



Sept. 10, 1957 'T0 CYCLO/VES AND PRODI/C T RECO VERY 2,805,980 FLUH)BATCH HYDROFORMING PROCESS Donald l). MacLaren, Scotch Plains, N. J.,assigner to Esso Research and Engineering Company, a corporation ofDelaware Appiication September 4, 1953, Serial No. 378,639 Claims. (Cl.196--49) The present invention relates to improvements in thelhydroforming of nap-hthas. More particularly, it relates to an improvediluid batch process utilizing noble metal catalysts.

Hydroforming is defined as an operation in which a petroleum naphtha iscontacted at elevated temperatures and pressures and in the presence ofa recycled hydrogencontaining gas with a solid catalytic material underconditions such that there is no net consumption of hydrogen.

Usually the feed stock boils substantially within the range of fromabout l50-430 F. and more particularly 200-350 F. The light ends, i. e.,the material boiling vfrom about 0-200 F., are not subjected to thisreaction because the virgin naphtha light ends already have a fairlygood octane rating and cannot be substantially improved without sueringan undue loss in yield. The feed or charging stock to the hydroformingreactor can be a virgin naphtha, a cracked naphtha, a Flscher-Tropschnaphtha, a mixture of these, -or the like.

Hydroforming opera-tions are `ordinarily carried out in the presence ofhydrogen or hydrogen-rich recycle gas at temperatures of 750-1150 F., inthe pressure range of about 50 to 1000 pounds per square inch with ahydrogen dilution of from 100 to 10,000 C. FJB. Noble metal catalysts,especially platinum, have been nding .increasing utility in theseprocesses because of their high activity. This platinum catalyst isusually supported on a suitable base, such as alumina, and may alsocontain a :small amount of promoters or stabilizers such as boria,phosphoric acid, silica, halides or organic acids. F or instance, acommonly used composition of such catalyst is one containing from 0.01to 2.0 weight usually about 0.5 weight percent platinum, the remainderbeing Vthe alumina lspacing agent or base. In place of alumina, otherbases having mild cracking activity are used.

The chemical reactions .involved in the hydroforming process includedehydrogenation of naphthenes to the corresponding aromatics,isomerization of straight chain paralns to form branched chainparaftins, isomerization of cyclic compounds `such as ethylcyclopentaneto form methylcyclohexane, and some aromatization, dealkylaticn andhydrocracking of paraiins. ln a hydroforming `operation which isconducted eiciently it is possible with the use of a proper catalyst andproper conditions of operation to hydroform va virgin naphtha having anoctane number of about 50 to a hydroformate having an octane number offrom 95 to 98 and obtain yields of Cs-lhydrocarbons as high as 85%.

It has been proposed in application Serial No. 188,236, filed October 3,1950, now U. S. Patent 2,699,823, issued September 21, 1954, to effectthe hydroforming of naphtha fractions in the presence of a denselluidized catalyst mass in a uidized solids reactor system in whichnaphtha vapors are passed continuously through the denser, fluidized'bed of hydroforming catalyst particles in a reaction zone, spentcatalyst particles being withdrawn continuously from the dense 'bed inthe reaction zone and passed to a Patented Sept. 10, 1957 separateregeneration zone where fouling, deactivating carbonaceous deposits areremoved by combustion, whereupon -the regenerated catalyst particles arecontinuously returned to the main reactor vessel. Fluid hydroforming, asthus conducted, has several funda-mental advantages over fixed bedhydroforming such as (1) the operations are continuous, (2) the vesselsand equipment can be designed for single rather than dual functions, (3)the reactor temperature is substantially constant throughout the bed,and (4) the regeneration or reconditioning of the catalyst may bereadily controlled.

In platinum catalytic processes, however, it is undesirable toregenerate more often than is absolutely necessary because the rate ofactivity decline during the feed portion of the cycle becomes faster.Thus while the catalyst is restored to initial activity and selectivityby each regeneration, each succeeding on feed cycle becomes shorter andshorter with each subsequent regeneration.

Important factors in the latter, for example, are the in-v creased sizeof the platinum crystals and the rate of platinum crystal growth.

In such cases it is undesirable to employ the conventional continuousfluid technique vbecause of the frequency with ywhich the catalyst isregenerated. Since activity `and selectivity reflect the average age,fluid operation tends to give lower activity and selectivity than isnormally obtained in Xed bed operation. However, it is highly desirableto `be able to take advantage of the isothermal nature of the fluid.system because of the adverse effect on activity maintenance of highinlet temperature encountered in fixed bed opera-tion. One way yofaccomplishing this would be to have two-batch fluid units. One of theunits is on regeneration While the other is on feed. In the case offluid platinum reforming where the catalyst is very expensive, it isobviously undesirable, however, to provide an eXtra charge of catalyst.

This invention provides an improved process for combining the advantagesof the isothermal iluid system in combination with the infrequentregenerations possible in Ibatch operation. As explained in furtherdetail below, two batch reaction vessels are provided with a transferline burner in between. When it is time to regenerate, the catalyst isslowly withdrawn from one reactor vessel and passes through the transferline burner where it is regenerated, carbon being removed, and thencharged into the second vessel. While this transfer is being made, feedentering the first reactor is also passed through the second reactor.Thus, no loss in overall feed rate is incurred during the regeneration.lt is thus possible to periodically regenerate the catalyst in thisbatch fluid system while providing only a ysingle charge of catalyst.

This invention vwill be better understood by reference to the flowdiagram shown in the drawing.

In the drawing, 1 is a reaction vessel provided near the bottom with aninlet line 2. -for the introduction of hot hydrogen-rich recycle processgas. A portion of the recycle gas can also be sent directly intosta-ndpipe 10. A perforated plate or distributor grid 3 is arrangedhorizontally Within the vessel for insuring uniform distribution of theincoming recycle gas over the entire cross section of the reactorvessel. A separate inlet line 4 connected to distributor grid 5 or thelike is shown for the introduction of naphtha above the grid member 3,although the fresh feed may, if desired, lbe introduced separately `or`along with recycle gas below the grid. The reactor vessel 1 is chargedwith nely divided hydroforming catalyst particles, and the superficialvelocity of the vapors and gases passing upwardly through the vessel isso controlled as to form a dense, fluidized, turbulent bed of catalyst 6having a definite level L superposed by a dilute or disperse phase 7comprising small amounts of catalyst contained in gaseous or vaporousreaction products. The reaction products are taken overhead from thereactor through line 8, through cyclone or cyclones 9 or the like forseparating entrained catalyst particles which are returned to the densebed 6 through the dip leg attached to the bottom of the cycloneseparator. Reaction products are conducted via line 8 through suitableheat exchange equipment to fractionating, stabilizing and/or storageequipment not shown.

After the operation has been carried on for a cer* tain period of timein the system just described, it becomes desirable to regenerate thecatalyst to remove carbon, restore its activity and selectivity. Whenthis becomes necessary, catalyst from dense bed 6 is Withdrawn throughthe standpipe 10, where it is picked up by a stream of air and carriedthrough the transfer line burner 11. Carbon is burned from the catalystin the transfer line burner, a conduit of restricted cross section. Thecatalyst is in the form of a confinedv stream. Catalyst is eparated fromthe regeneration gas in cyclone yseparator 12 and is subsequently fed toreactor vessel 13 through transfer line 14 where it forms a dense bed15. Regenerator gas is withdrawn through line 24.

During this burning operation in order to prevent reduction of feed rateor cessation of reforming operation, overhead products including feedleaving reactor 1 are diverted from the normal product recoveryfacilities and are fed directly via line 16 to the bottom of reactor13,A

where the remainder of the reforming operation is completed. In reactor13 a dense, fluidized turbulent bed of catalyst is formed similarly tothe operation in reactor 1. The catalyst has a definite level L'superposed by` a dilute or disperse phase 17. A perforated plate ordistributor grid 18 is also arranged horizontally Within reactor 13, asis a distributor 19. The superficial velocity of the vapors enteringthrough line 16 is such as to form the dense, uidized, turbulent bed ofcatalyst 1S. Reactor 13 is thus designed similarly to reactor 1. Thereaction products are taken overhead through a cyclone separator 20where entrained catalyst particles are returned to the dense bed 15`through dip pipe 21. Reaction products are conducted via line 22-through suitable heat exchangel equipment to fractionating, stabilizingand/or storage equipment not shown.

During regeneration of the catalyst in reactor 1 the level L in reactor1 goes down as catalyst is Withdrawn until eventually reactor 1 isempty. Atl this point the feed and recycle gas are no longer admitted toreactor 1, but are switched to reactor 13, the feed entering throughdistributor ring 19 and recycle gas through line 23. Operation accordingto the batch fluid technique then proceeds until it becomes necessarytoregenerate again. At

that point the reaction in reactor 13 exactly parallels theV reactionoperations that previously were conducted in reactor 1. Lines can beprovided, as apparent to those skilled in the art, for conductingproduct from reactor 13 over to reactor 1 When it becomes necessary toregenerate again in a similar manner as already described for reactor 1.

The feed stock is preheated alone or in admxture with recycle gas toreaction temperature or to the maximum temperature possible Whileavoiding thermal degra dation of the feed stock. Ordinarily preheatingof the feed stock is carried out to temperatures of about 800- l000 F.,preferably about 950or F. The naphtha preheat should be as high aspossible While avoiding thermal degradation thereof as by limiting thetime of residence in the transfer or feed inlet lines. The preheatedfeed stock may be supplied to `the reaction vessel in admixture withhydrogen-rich recycle gas, or lit may be introduced separately as shown.The recycle gas, whichk contains fromabout 60 to 95 volume percenthydrogen, is preheated to temperatures of about 1150'-l'200 F., prior tothe introduction thereof into inlet line 2. `The recycle gas should becirculated through the reactor at a rate of from about 100 to 10,000cubic feet per barrel of naphtha feed. The amount of recycle gas addedispreferably the minimum amount that will keep carbon formation at asatisfactory low level and supply the necessary heat of reaction overand above that supplied by other means such as heating coils, heatedshot, etc.

The reactor system is charged with a mass of finely divided hydroformingcatalyst particles. The noble metal catalysts for treatment inaccordance with the present 'inventionk include platinum, palladium,gold, silver, iridium, rhodium, ruthenium, asmium, etc. These noblemetals are generally associatedV and supported on a metal oxide andparticularly an oxide of a Vmetal in the left hand columns of groups IIIto VIH of the periodic table including particularly the oxides ofsilicon, aluminum, titanium, zirconium, hafniumthorium, vanadium,tantalum, chromium, molybdenum, tungsten, uranium, manganese, zinc,cobalt, nickel, etc. It is understood that the catalyst can comprise twoor more noble metals and/or two or more metal oxides. In still othercases one or more ac-l tivating components may be included in thecatalysts. Particularly suitable is the platinum on alumina catalyst.

As explained, the carbonaceous deposits are removed from the catalyst ina transfer line burner when regeneration becomes necessary. This isaccomplished by adding air to the burner in admixture with sufficientrecycled flue gas to control temperature in the range of 700- 1150 F.,preferably about l050 F. Residence time in vthe transfer line is in theorder of l to l0 seconds or longer.

The catalyst particles are, for the most part, between 200 and 400 meshin size, or about 0-200 microns in diameter, with a major proportionbetween 20 and 80 microns.

Space velocity or the weight in pounds of feed charged per hour perpound of catalyst in the reactor depends upon the age or activity levelof the catalyst, the character of the feed stock, and the desired octanenumber of the product. Space velocity for a platinum on alumina catalystmay Vary, for example, from about 1.5 Wt./hr./wt. to about 0.15Wt./hr./wt. Space velocity also depends -to a very large extent on thereactor temperature and recycle gas rate.

fIn order to explain the invention more fully, the following conditionsof operation of the Various components are set forth below and in theexamples. I Conditions in reactors l and 13 Preferred Range Catalystcomposition 0.5% Pt on A1205 0.01-2.0% Pt.

emp., F S50-950 750-1,150. Pressure, p. s. i. g 50-500 04,000. Spacerate, lbs. feed/1b. cat/hr .5-10. .1-20. Culft. 0f recycled gas fed/bbl.0f 1,000-6,000. 100-10,000.

o Y Concentration of H2 in recycle 80-90 60-95.

gas.

Conditions in transfer line regenerator Il Preferred Range Temperature,F Y 1, OOO-1, 100 700-1. 150 Pressure, p. s. i. g 50-500 0-1,000Residence time, Seconds 1-10 1-60 Fluidizng gas velocity, fia/sec 10-305-100 What is claimed is:

l. In a process for hydroformng hydrocarbons in contact with a dense,udized catalytic mass wherein the catalyst comprises a supported noblemetal, the improvement which comprises the steps of periodicallywithdrawing carbonized catalyst particles from a dense fluidized bed ofcatalyst particles in a first hydroforming reaction zone, regeneratingthe withdrawn catalyst particles by treatment with an oxygen-containinggas at elevated temperatures While the catalyst particles are in theform of a conned stream, separating the regenerated catalyst particlesfrom the regeneration gas, discharging the separated regeneratedcatalyst particles into a second hydroformng reaction zone, withdrawingproduct and feed vapors overhead from said rst reaction zone andsimultaneously with the said withdrawal and regeneration of thecarbonized catalyst passing the vapors removed overhead from said firsthydroforming zone into the bottom of said second hydroforming reactionzone, contacting the said vapors with a dense uidized bed of saidcatalyst particles in 20 said second hydroforming reaction zone for aperiod suicient to complete the hydroforming reaction and withdrawinghydrofornied products overhead from said second hydroforming reactionzone.

2. The process of claim 1 in which the regeneration step is carried outat a temperature in the range of 1000 1100 F.

3. The process of claim 2 in which the time of the regeneration step isin the range of l-10 seconds.

4. The process or" claim 1 in which the catalyst is platinum on alumina.

5. The process of claim 4 in which the catalyst is 0.5 Weight percentplatinum on alumina.

References Cited in the tile of this patent UNITED STATES PATENTS2,430,245 Payne Nov. 4, 1947 2,479,110 Haensel Aug. 16, 1949 2,642,381Dickinson June 16, 1953

1. IN A PROCESS FOR HYDROFORMING HYDROCARBONS IN CONTACT WITH A DENSE,FLUIDIZED CATALYTIC MASS WHEREIN THE CATALYST COMPRISES A SUPPORTEDNOBLE METAL, THE IMPROVEMENT WHICH COMPRISES THE STEPS OF PERIODICALLYWITHDRAWING CARBONIZED CATALYST PARTICLES FROM A DENSE FLUIDIZED BED OFCATALYST PARTICLES IN A FACT HYDROFORMING REACTION ZONE, REGENERATINGTHE WITHDRAWN CATALYST PARTICLES BY TREATMENT WITH AN OXYGEN-CONTAININGGAS AT ELEVATED TEMPERATURES WHILE THE CATALYST PARTICLES ARE IN THEFORM OF A CONFINED STREAM, SEPARATING THE REGENERATED CATALYST PARTICLESFROM THE REGENERATION GAS, DISCHARGING THE SEPARATED REGENERATEDCATALYST PARTICLES INTO A SECOND HYDROFORMING REACTION ZONE, WITHDRAWINGPRODUCT AND FREED VAPORS OVERHEAD